Method of improving the efficiency of fat separation in the separation of a liquid food product

TECHNICAL FIELD

The present invention relates to a method of improving the efficiency of fat separation in the separation of a liquid food product of a certain fat content, comprising the steps that the liquid food product is caused to pass at least two separators connected in parallel, a first and a second separator, each with an inlet conduit for product and in which separators the product is divided up into a lighter phase and a heavier phase, and that the first separator is regulated so that the lighter phase has a fat content which is less than 15%.

BACKGROUND ART

Separation is an industrial process which is often used in the food industry. Fat separation by such a process is used, for example, for milk and whey. The separation normally takes place in a centrifugal separator.

In its interior, the separator has a number of conical inserts disposed in a stack with a well-defined spacing between the inserts. The inserts are provided with distribution holes which are vertically disposed. Through these holes, the milk or whey arrives from the inlet into the separation section proper and is subjected to centrifugal force. Particles and impurities in the milk or the whey move outwards along the surfaces of the inserts and are accumulated in a sediment tank. The lighter phase of the liquid food, i.e. the fat/the cream, moves inwards along the surfaces of the inserts towards the rotation shaft and is conveyed out from the separator through an axial outlet. The heavier phase, which may consist of skimmed milk or whey which has been freed of fat globules, moves outwards along the surfaces of the inserts and is accumulated to an outlet. Modern separators may have different constructive concepts. The present invention may be employed for all types of centrifugal separators.

One common area of use for the separation process is the separation of milk, where the milk is separated into a skimmed milk phase and a cream phase. Thereafter, the milk may be standardised, for example to consumer milk possessing the desired fat content, in that a part of the cream phase is recycled back to the skimmed milk phase.

The separation process is also employed to extract fat from whey. Whey is a by-product in cheesemaking and, since roughly a third of the world's milk production is used for cheesemaking, this implies that almost a third of all milk becomes whey. Whey, which had previously only been employed as animal feed and as fertilizer, risked becoming an environmental problem. Today, whey has more or less come to be considered as a valuable raw material in the production of protein with a high nutrient value. The fat which is extracted from the whey is normally recycled to the cheesemaking process or to other parts of the dairy process.

It is an attractive option to increase the fat separation in all separation processes, above all in the separation of whey. By separating off more fat from the whey, a more efficient and more economical process can be obtained in a later production of protein.

Earlier attempts to increase the yield in the light phase, i.e. to extract more fat from the milk or whey have involved the use of larger separators. Larger separators imply larger capital costs, both as investment costs and as operational costs.

Swedish Patent Specification SE 526828 describes a method for improving the efficiency of the fat separation in whey separation. The whey is separated in a first separator or alternatively several separators. The light phase from this or these separators is thereafter separated in a second separator. In order to obtain a good level of capacity for this method, at least two first separators are required, whereafter an additional separator is also required.

OBJECT OF THE INVENTION

One object of the present invention is to realise a method which renders further economical the separation of fat from a liquid food product, in that only two separators are necessary for carrying the method into effect.

SOLUTION

This and other objects have been attained according to the present invention in that the method of the type described by way of introduction has been given the characterising feature that the lighter phase from the first of the separators connected in parallel is led into the inlet conduit to the second of the separators connected in parallel.

Preferred embodiments of the present invention have further been given the characterising features as set forth in the appended subclaims.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

One preferred embodiment of the present invention will now be described in greater detail hereinbelow, with reference to the accompanying Drawing, in which:

FIG. 1 illustrates a flow diagram for separation according to the present invention.

The Drawing shows only those parts and details essential to an understanding of the present invention, the placing of the separation process in a food plant, which is well-known to a person skilled in the art, having been omitted.

DESCRIPTION OF PREFERRED EMBODIMENT

FIG. 1 shows a flow diagram for a separation process according to the present invention. The separation process comprises at least two separators 1, 2 connected in parallel. Three or more separators 1 connected in parallel may also occur. The separators 1, 2 are centrifugal separators and they may consist of all constructions known on the market.

The food product may be raw milk with a fat content of 3.5-8.5%, or alternatively whey which normally has a fat content of 0.2-0.4%. Milk is normally separated at a temperature of 40-60° C., but lower temperatures may also occur. The whey is at the temperature which it has when it leaves the cheesemaking tank, normally 30-50° C. Processes which result in higher temperatures may also occur.

Each of the two separators 1, 2 connected in parallel has a conduit 3, 4 which leads the liquid food product into each respective separator 1, 2. In the separators 1, 2, the product is divided into a lighter and a heavier phase, at the same time as particles and impurities are removed from the product. The heavier phase, which consists of skimmed milk, or alternatively fat-free whey, leaves the separators 1, 2, through a conduit 5, 6, respectively. The conduits 5, 6 from the separators 1, 2 connected in parallel are united into a common conduit 7 for further treatment of the heavier phase. When the method is employed for whey, the heavier phase has a fat content which in many cases is lower than 0.05%. The fat content of the heavier phase is dependent upon the process.

The lighter phase, which consists of cream or fat from the whey, leaves the one 1 of the separators connected in parallel through a conduit 8. The conduit 8 leads to the inlet conduit 4 which provides the second 2 of the separators connected in parallel with product.

The product, when it consists of whey, has a fat content of 0.2-0.4% when it enters into the inlet conduit 3, 4 of each respective separator 1, 2. When the second separator 2 has an increased inlet flow in that the light phase from the first separator 1 is supplied to the inlet conduit 4 of the second separator 2, the second separator 2 will be supplied with a product which has a fat content of 0.4-0.8%.

The first separator 1 is regulated so that the lighter phase has a fat content of less than 15%. Preferably, the lighter phase has a fat content of 1-8%. This is achieved by increasing the flow in the lighter phase, which entails that a larger number of smaller fat globules accompany the lighter phase which passes out through the conduit 8.

The lighter phase which leaves the second separator 2 through the outlet conduit 9 has a fat content of up to 40%.

If three separators 1, 2 are employed in the process, the lighter phase from two separators 1 is converged and led into the inlet conduit 4 of the third separator 2. If use is made of four separators 1, 2, two separators may operate in tandem in accordance with the above described method for two separators. Thereafter, each respective phase is converged. Alternatively, the light phase is converged from three or more separators 1 to the inlet conduit 4 to an additional separator 2. The heavier phase from all separators 1, 2 is converged to one conduit 7.

Despite the apparently slight quantities of increased fat separation, the method according to the present invention entails that there will be an increase of fat separation by 5-10% for a normal food plant. In addition to obtaining an increased quantity of fat as yield, there will be obtained, above all as regards whey, a heavier phase which has a smaller residual fat content than in conventional fat separation. This heavier phase constitutes a raw material for valuable protein extraction. In the protein extraction, it is a major advantage, and entails major savings, to have a lower residual fat content. A lower residual fat content of the whey, reduces not only investment costs but also running costs for a protein extraction plant.

The increased quantity of fat also has a commercial value. Either as an increased volume of cream or as an increased quantity of fat from whey which is normally recycled back to the cheesemaking process.

As will have been apparent from the foregoing description, the present invention realises a method which, in a simple and economical manner, improves the efficiency of separation of a liquid food so that there will be obtained an increased separation of fat. The increased separation of fat affords major advantages in subsequent processes, above all when the food product consists of whey.

The present invention should not be considered as restricted to that described above and shown on the Drawing, many modifications being conceivable without departing from the scope of the appended Claims.